Enhancing CO2 Fixation and Wastewater Treatment Performance by Assembling MgFe-LDH on Chlorella pyrenoidosa

Microalgae are considered to be a dual solution for CO2 fixation and biogas slurry purification due to their high photosynthetic efficiency and strong environmental adaptability. However, their application is constrained by the low solubility of CO2 in the solution environment, which restricts microalgal growth, resulting in low biomass production and poor slurry purification efficiency. In this study, we developed MgFe layered double hydroxide (LDH) that spontaneously combined with Chlorella pyrenoidosa to help it concentrate CO2, thereby increasing biomass yield and purification capacity for food waste biogas slurry. The prepared MgFe-LDH exhibited a typical layered structure with a CO2 adsorption capacity of 4.44 mmol/g. MgFe-LDH and C. pyrenoidosa carried opposite charges, enabling successful self-assembly via electrostatic interaction. Compared with the control, the addition of 200 ppm MgFe-LDH increased C. pyrenoidosa biomass and pigment content by 36.82% and 63.05%, respectively. The removal efficiencies of total nitrogen, total phosphorus, and ammonia nitrogen in the slurry were enhanced by 20.04%, 31.54% and 14.57%, respectively. The addition of LDH effectively alleviated oxidative stress in C. pyrenoidosa and stimulated the secretion of extracellular polymeric substances, thereby enhancing the stress resistance and pollutant adsorption capabilities. These findings provided a new strategy for the industrial application of microalgal technology in CO2 fixation and wastewater treatment.